Electrochemical studies on the corrosion of electrically conductive sulfide minerals in high pressure hydrothermal fluids - A case study from pyrite

Abstract

Electrochemical data concerning electrically conductive sulfide minerals submitted to high pressure hydrothermal fluids above 150 °C has not been reported in spite of its significance. In this work, electrochemical impedance spectroscopy (EIS) and Tafel studies of pyrite corrosion in pure water, 3.5% NaCl solution and 0.1 M sulfuric acid with 1796 kPa O2 at 350 °C, 30 MPa were conducted, with the assistance of a self-designed three-electrode electrochemical measurement set-up that can operate in high pressure hydrothermal fluids. Results show that in pure water, 3.5% NaCl solution, and 0.1 M sulfuric acid with 1796 kPa O2, corrosion potential (Ecorr) is respectively -150, -334 and -752 mV, corrosion current (Icorr) is respectively 1.44E-5, 1.95E-4 and 7.73E-3 A. The solid-liquid interface information at pyrite surface achieved by EIS measurements reveals an important reason of the difference between the values of Ecorr and Icorr in the three studied fluids. The electrochemical studies in this work also provide a promising method for research into the corrosion of other conductive sulfide minerals in high pressure hydrothermal fluids.